The present invention relates to a method of putting articles into a queue and to apparatus enabling the method to be implemented.
The invention applies particularly to separating parcels in bulk, e.g. postal parcels, so as to form a queue of parcels disposed sequentially (i.e. one behind another).
U.S. Pat. Nos. 5,918,723 and 5,950,800 in particular disclose apparatus for xe2x80x9csingulatingxe2x80x9d articles (i.e. putting them into a queue) in which the apparatus is essentially constituted by a plurality of conveyors extending perpendicularly relative to one another, and generally driven at increasing speeds going from an inlet towards and outlet of the apparatus, which conveyors are associated with ramps and/or static deflectors for guiding the articles.
Those apparatuses suffer from the drawback of causing the articles to drop on being transferred from one conveyor to another, and that can damage fragile articles; furthermore, the apparatus is generally bulky, because of the presence of deflectors and also the presence of return conveyors (recycling conveyors) which convey articles that have been separated out from the stream of articles treated by the apparatus to take them from the downstream end thereof back towards the upstream end; this gives rise to a loss of energy and also to the recycled articles being subjected to additional impacts on being delivered by the return conveyor back to the inlet to the apparatus.
In above-mentioned document U.S. Pat. No. 5,950,800, the apparatus includes a conveyor sloping at an angle of at least 25xc2x0, thereby causing articles which are piled up one on another to drop so as to ensure that the articles delivered at the outlet from the conveyor occupy a single layer only.
Document U.S. Pat. No. 4,634,328 discloses apparatus for putting articles into a queue, which apparatus comprises:
two conveyors for conveying articles, namely an inlet conveyor and an outlet conveyor, which conveyors are disposed substantially in line one with the other;
a plurality of parallel fingers which can be displaced by actuators and which extend vertically between the two conveyors so that depending on their position they can allow or prevent articles from passing from one conveyor to the other;
a camera disposed to observe articles present on an inlet conveyor;
a computer algorithm for determining the profiles of the articles observed by the camera;
a robot suitable for pushing articles selectively one by one from the first conveyor to the second; and
a controller connected to the camera, to the robot, and to the finger-displacing actuators so as to respond to the profiles of the articles by controlling displacement of the fingers in order to bring them into a position in which they allow one article to pass while preventing other articles from passing, and then to control the pusher robot to transfer the articles one by one from the first conveyor to the second.
An object of the invention is to propose a system for separating articles that is simpler than the apparatus described in the above document.
An object of the invention is to propose a system for putting articles into a queue that remedies the drawbacks of known methods and apparatuses, at least in part.
In a first aspect, the present invention consists in providing apparatus that comprises a plurality of parallel transfer conveyors which are suitable, together or separately, for transferring an article from the outlet of an inlet conveyor to the inlet of an outlet conveyor, between which and in line with which the transfer conveyors extend, and which includes a camera for observing articles on the inlet conveyor and means for deriving article outline and identity data from images taken by the camera, and means for selectively actuating the transfer conveyors as a function of said outline and identity data.
In other words, the invention consists in using a xe2x80x9cmultibeltxe2x80x9d conveyor interposed between an inlet conveyor and an outlet conveyor and having a plurality of belts extending parallel and side by side, each forming a transfer conveyor; each belt is suitable for being driven individually under the control of an electronic control unit, as a function of data that results from identifying the outline of an individualized article, which outline is obtained by processing one or more images taken by a camera for observing the articles present on the inlet conveyor; an individualized article selected from a plurality of articles presented broadside by the inlet conveyor at the inlet to the multibelt conveyor is transferred by actuating the belts which lie in line with said individualized article differently compared with how the belts are actuated which do not lie in line with said individualized article; this xe2x80x9cdifferentialxe2x80x9d actuation of the various parallel belts of the multibelt conveyor can be performed in two fundamentally different manners:
either by actuating said belts that lie in line with the selected individualized article while keeping the other belts stationary (on/off operation);
or else by actuating said belts that lie in line with the selected individualized article at a first transfer speed while still actuating the other belts at least at a second transfer speed of a value that is different from that of the first transfer speed, and in particular is less than said first transfer speed.
These two modes of actuation can be combined.
By means of this system, when a plurality of articles are presented side by side (broadside-on) at the outlet from the inlet conveyor, said individualized article selected from said plurality of articles is detached (separated) from said plurality on being transferred by the multibelt conveyor to the outlet conveyor so that it is presented at the inlet of the outlet conveyor before any other article in said plurality; a second article in said plurality is then selected and the belts are then controlled to move differentially in a manner that is adapted to the position and to the outline of said second selected article, as determined from the image of the transverse profile of the group of articles remaining on said first conveyor, thus enabling the second article to be separated from the plurality of articles present on the inlet conveyor in the same manner as the first selected article was separated therefrom.
With these operations being repeated as many times as there are individualized articles present at the inlet to the multibelt conveyor, it is possible to separate the articles (longitudinally) so that the multibelt transfer conveyor presents these articles one after another to the outlet conveyor; where appropriate, they can then be placed in a queue (one behind the other) e.g. by using a vertical deflector extending in a plane that slopes a little relative to the vertical longitudinal plane of the outlet conveyor.
Thus, in another aspect, the invention consists in a method of separating a group of articles in bulk that are presented broadside-on on an inlet conveyor, which method comprises:
taking an image of the group of articles;
determining the number of articles in the group and the outline of each article by computation on the basis of the image, thereby making it possible to determine the position and the width of the base of each of the articles in a transverse vertical plane; and
controlling the belts or parallel groups of belts of a multibelt conveyor that extends said inlet conveyor to advance in non-uniform manner (at different speeds and/or at different times) so as to correspond to each of the individualized articles respectively, in such a manner that the articles in the group of articles are presented at the outlet from the multibelt conveyor with longitudinal offsets between articles forming successive pairs of articles.
The mean speed at which articles are conveyed is preferably maintained at a value lying in a range going form 0.1 meters per second (m/s) to 2 m/s.
The method and the apparatus of the invention make it possible to avoid dropping articles and to avoid recycling them.
The system of the invention advantageously replaces the system described in U.S. Pat. No. 4,634,328; in the apparatus of the invention it matters little if an article for sorting presents density that is not uniformly distributed in three dimensions (as is frequently the case for packaged articles): by conveying a non-uniform article on a plurality of adjacent belts of a multibelt conveyor with the article resting on said belts, it is possible to ensure that the article is conveyed with rectilinear movement in translation along the longitudinal axis of the multibelt conveyor; in general, such movement is unlikely to cause the conveyed article to bear against adjacent articles in the group, where that might otherwise cause the articles that bear against one another to rotate (and/or move sideways).
In contrast, the pusher robot of the above-mentioned patent is not only complex in structure and to control, but it is naturally confronted with difficulties when controlling the path of an article that it is pushing: it is not possible from the image of a non-uniform article to deduce the position of its center of gravity or to deduce the characteristics (modulus and direction) of the resultant of the friction forces opposing sliding of the article on the member (conveyor belt) that is supporting the article; consequently, when using the apparatus as described in U.S. Pat. No. 4,634,328, the thrust force imparted by the robot tends to cause the article to rotate and/or tilt, thereby making it liable to interfere with (strike) the fingers interposed between the two conveyors; in addition, the path followed by the article pushed by the robot is modified by the reaction forces that result from the pushed article bearing against the fingers and/or against other articles surrounding it.
Furthermore, the use of a multibelt conveyor makes it easier to transfer articles that are deformable (such as newspapers) and to transfer articles that might roll, in particular articles that are approximately cylindrical or spherical in shape, by giving them a conveyor path that is determined and controlled and in longitudinal translation without the article being turned or pivoted, unlike the pusher robot.